Along with the ever-increasing demands for multimedia service, studies have recently been conducted on communication technologies for increasing data rate in wireless communication systems. For example, the communication technologies include Institute of Electrical and Electronics Engineers (IEEE) 802.11 Wireless Local Area Network (WLAN) and IEEE 802.16 Wireless Metropolitan Area Network (WMAN).
WLAN, an extension of wired LAN based on IEEE 802.11, is a short-range communication technology developed to provide high-speed communication services to stationary users in a limited crowded area such as outdoors or downtown. A network supporting the WLAN technology (referred to as a WLAN network) supports data rates ranging from tens of Mbps to hundreds of Mbps to users within a service area. However, the WLAN network does not ensure mobility to users and covers a limited service area.
WMAN provides data service to users that are stationary, walk, and move at a medium speed of up to 60 km/h according to IEEE 802.16. A network supporting the WMAN technology (referred to as a WMAN network) supports average data rates of tens of Mbps. The WLMAN network ensures mobility to users and covers a wide service area.
As described above, in the case where a wireless communication system supports multiple networks owing to the development of communication technology, the networks have different characteristics.
Therefore, for the wireless communication system to select a network according to the type of a user-requested service and provide it to users, the networks should interwork reliably. That is, the wireless communication system should support seamless handover between heterogeneous networks or media.